From the viewpoint of controls on noise of an automobile, a demand recently exists for tranquility particularly in relation to an engine sound. Tranquility is enhanced by means of attaching an acoustic insulator to an engine room and an exhaust line. Moreover, in view of an emphasis on fuel-economy performance, a design is made so as to reduce an engine speed and an engine sound.
However, such enhanced tranquility cannot necessarily be said to be a comfortable drive environment for passengers of the automobile. Put another way, there are cases the circumstance where a moderate engine sound is heard in a vehicle cabin is a more comfortable drive environment for a driver, such as a motoring enthusiast.
In order to meet the taste of such a motoring enthusiast, a device for artificially generating an engine sound in the vehicle cabin has already been proposed.
Devices proposed as such a device include; for instance, a device capable of generating a sinusoidal waveform or a pulse sound in tune with an engine speed (synchronized with an engine sound), emitting the thus-generated sinusoidal waveform or pulse sound in a vehicle cabin, to thus add the waveform or pulse sound to an engine sound actually leaked into the vehicle cabin, thereby enabling passengers to hear in an enhanced manner a portion of the frequency band of the engine sound (see; e.g., Patent Document 1); a device which has previously recorded a desired engine sound and plays the thus-recorded sound back in tune with the engine speed, thereby producing a desired engine sound in a vehicle cabin (see; e.g., Patent Document 2); and a device which picks up an engine sound in a vehicle cabin by means of a microphone embedded in a headrest and enables a passenger to hear in an enhanced manner a portion of the frequency band (see; e.g., Patent Document 3).
Patent Document 1: JP-A-5-80790
Patent Document 2: JP-A-7-302093
Patent Document 3: JP-A-2004-74994